The lawmakers' blast came after the Justice Department refused to let Barbara Bosserman, a lawyer and Democratic donor involved in the department's IRS investigation, go before Jordan's economic growth subcommittee next Thursday, The Hill reported.

In a letter, Deputy Attorney General James Cole told the Ohio lawmaker letting Bosserman get grilled about on an open Justice Department investigation would break "longstanding policy" to not provide Congress with "non-public information about ongoing criminal investigations," The Hill reported.

But to the Republican lawmakers, the rejection was just the latest evidence the Justice Department and FBI are hampering their own investigation of the scandal.

"The Justice Department's refusal to answer questions — including questions about apparent conflicts of interest within the investigation itself — is highly disappointing,” an House Oversight spokesman told The Hill.

“This refusal only enhances concern that politics have infected the Administration's examination of inappropriate targeting by the IRS."

In his letter, Cole insisted the questioning would cross the line, The Hill reported.

“Members of Congress have long understood and respected the department's strongly-held concern that subjecting line prosecutors to congressional questioning poses significant risks to the department's law enforcement efforts and would have a chilling effect on department attorneys,” he wrote.

On Wednesday, Attorney General Eric Holder rejected reports there would likely be no criminal charges in the IRS targeting.

He also dismissed the call by Republican Sen. Ted Cruz to to appoint a special prosecutor to investigate the IRS targeting, saying it wasn't necessary.